In general, the invention relates to packaging materials of the type made of relatively thin flexible plastic film or sheet material and, more particularly, to packaging wrappers made of one flat sheet of such material for wrapping about and enclosing articles to be packaged. The present invention is particularly adapted for packaging of produce which requires ventilation and involves a new form of expandable slit pattern usable in various kinds of packaging materials such as bags, boxes and covers as well as wrappers.
One use of a wrapper of the type of this invention is in connection with wrapping of lettuce as disclosed in my prior U.S. Pat. No. 3,762,629. An advantage of the present invention is that the shape of the slits and the location of the slits relative to one another enables expansion of the slitted portion of the wrap in a new manner providing greater expansion than with prior art slit patterns of the type illustrated in U.S. Pat. Nos. 3,040,968, 3,067,039, 3,069,067, 3,109,579, 3,245,606, 3,550,842, 3,603,369, 3,655,501 and 3,762,629. As a result, larger heads of lettuce may be more easily wrapped with smaller size wrapper sheets and, if desired, the size of the wrapper sheets may be reduced to achieve the same kind of wrapping results achieved with prior art slit patterns on larger size wrapper sheets. In addition, the shape of the slits and the location of the slits relative to one another provides for expansion between slits in a new manner increasing the amount of expansion and reducing the likelihood of tearing between the slits. As a result, thinner gauge plastic sheet may be utilized without encountering tear problems as might be encountered with prior art slit patterns. The foregoing advantages are of substantial importance since the cost of plastic sheet and film materials has greatly increased in recent times.
Another advantage of the present invention involves the size and configuration of the openings produced in the plastic sheet material when the slit pattern has been expanded. In the present invention, the openings are of generally polygonal shape in the fully expanded position of the slit pattern and are of relatively large size while providing adequate retention of the contents of the wrapper. The large size of the openings permits adequate ventilation of the contents of the wrapper and facilitates the application of moisture to the contents as by spray techniques. In addition, the slit pattern of the present invention provides a new appearance in the fully expanded condition which is more attractive than prior slit patterns in that it provies a crisp sparkling appearance. Furthermore, when the slit pattern of the present invention is fully expanded, interconnected ribbon portions of the wrapper between the slits tend to turn 90.RTM. relative to the surface of the contents rather than laying flat against the surface of the contents as in prior art slit patterns so that the interconnected ribbon portions of the wrapper between the slits extend generally transversely at right angles to the periphery of the contents wrapped in the wrapper. Thus, more of the surface of the contents is exposed and the generally transversely extending interconnected portions of the wrapper act as vanes to catch and trap moisture applied to the contents, create a glittering effect by reflection of light, and also act as cushions between adjacent similarly wrapped articles such as lettuce on display in a bin at a store.
Another advantage of the present invention is that the cushion effect created by the transversely extending interconnected ribbon portions also provides a pleasing "fresh produce feel" when lettuce is handled by a customer due to the unique slit arrangement produced from parallel rows of longitudinally and transversely aligned generally step-shaped slits. When the sheet is stretched around a generally spherical object, such as a head of lettuce, the ribbon portions defined between adjacent pairs of slits twist and turn on edge so that flexible easily deflected flange portions on some of the ribbon portions extend transversely outwardly from the wrapper in position for several of them to engage the hand of a customer when the wrapped lettuce is held by the customer.
Accordingly, it is an object of the present invention to provide a novel and improved slit pattern for produce wrappers and the like having improved expansion characteristics and providing large openings for ventilation and application of water to the contents as well as facilitating viewing and touching of an article or articles covered thereby.
Another objective of the invention is to provide a produce wrapper having a unique appearance and cushioning effect.
Still another objective is to provide a produce wrapper which, upon being stretched in a direction to open the generally step-shaped slits, will cause ribbon-like portions formed therebetween to twist and turn on edge so as to protrude transversely relative to the surface of the wrapper and the contents thereof.
An additional object is to provide a produce wrapper having a centrally located slit pattern adapted to produce a multitude of variously angled light reflecting surfaces when stretched in a direction to open said slits.
Further objects of the invention forming the subject matter hereof are to provide a produce wrap slit pattern that is versatile, easy to use, relatively strong, readily adaptable to various plastic sheet materials and one that is distinctive as well as decorative in appearance.